DS is in Year 10 and in one of the 2 (equal) top maths sets. The teacher of the "other" top set is a member of the SMT and therefore has responsibilities beyond maths teaching.
Of the three maths lessons so far this year
Lesson 1: DS's set was taught by his teacher; the other set were taught by their teacher
Lesson 2: DS's set was taught by his teacher; the other teacher was involved in mgt things and his set had "independent learning"
Lesson 3: DS's set had independent learning while their teacher taught the other top set (actual teacher involved in mgt things).
One of DS's friends is in the "other" set and had the same teacher last year, and has told DS that this pattern of teaching is quite usual between the 2 top sets (DS was in a lower set last year so no first hand experience).
Obviously it's early days so far, but (depending on how many lessons are actually missed) is this considered an acceptable/normal way to manage the teaching of students in KS4)? I'm presuming as the DC are "top set", they are considered more able to work unaided?
(if it matters, this is not a top achieving school, there are 9 sets - only 4 of which will likely take the higher paper, and DC in the top 2 sets will be expected to get a 6+ at GCSE)